1. Field of the Invention
The invention relates to a safety strip as a connecting block for a striking edge or closing edge protection device or switch pad with an electrical switching device.
2. Description of the Prior Art
In EP 0 234 523 B1, which forms the class for the independent claims, is described a striking edge protection device with a safety strip, wherein the holding bodies (here called contact rollers) consist in each case of cylindrical rollers, the contact rollers meeting each other in a productive manner at the front-end points of contact. These holding bodies display contact elements, which in the class-forming literature passage are described as sleeves consisting of copper or nickel silver. The holding bodies are acted on by an elastic prestress through the fact that arranged in the interior of the contact rollers is an elastic cord that forces the individual contact rollers, and thus the holding bodies, in an axial direction against each other. Arranged between the individual holding bodies are insulating rings, which are arranged between the individual holding bodies with projecting wedge surfaces oriented radially with respect to the insulating-ring axis. In the event of a force oriented preferably transversely with respect to the longitudinal extension of the contact chain, only a minimum of wedging effect between the contact elements and the insulating ring results in an interruption of the closed-circuit current, which leads to a switching function within the switching device. After unloading of the contact chain, an automatic neutral position for closing the closed-circuit current circuit occurs. For the sensitivity of the response, the degree position of the collaborating wedge surfaces is essential.
With this known apparatus it is scarcely possible to construct safety strips that must be installed in a small radius, for example around a central pipe, in order to serve as a striking protection device.
For this application case, the use of the spheres from FR 21 35 922 A5 as contact elements is also not applicable. In this arrangement, the spheres do not center themselves in the soft hose, but rather, in order to make way for the prestress generated through the hose, the spheres shift against each other, so that a straight-line sphere chain is not present in the installed state.
Characteristic of both of the arrangements belonging to the prior art is the fact that a separation of the points of contact occurs in the case of a striking load upon the safety strip in a direction transverse to the longitudinal axis of the safety strip; for example, in the case of EP 0 234 523 B1 the elastic cord is stretched and in the case of the device according to FR 21 35 922 A5 the elastic hose is elongated.
Described in EP 421048 B1 is a safety strip that is to be used as a switch pad, wherein a multitude of contact elements and wedge elements are provided that are pulled against each other by means of an elastic cord. The wedge elements are formed as wedge plates and the contact elements as contact plates, whereby in the switching-ready state the elastic cord lies at different heights in the contact plates and in the wedge plates.